Sheet feeding apparatus

ABSTRACT

Sheet feeding apparatus is disclosed in which a movably mounted supporting tray supports a stack of sheets at one end of a desired path of feed. The tray has a vertically movable discharge end which is resiliently urged upwardly toward a retaining stop located at a fixed or constant vertical position. Thus the upper surface of the topmost sheet in the stack engages the stop and limits the upward movement of the tray discharge end, so that a common pre-feeding position is defined for the discharge end of each successive topmost sheet. A starting feed roller is mounted above the tray for movement between an upper non-feeding position, in which it is out of engagement with the stack of sheets, and a lower feeding position, in which the roller engages the upper surface of the topmost sheet and starts it along the path. Operating means for moving the starting feed roller from non-feeding to feeding position includes a resilient connection which insures resilient feeding engagement of the roller with the topmost sheet, while the tray discharge edge is urged upwardly with sufficient resilient force to feed the discharge end of each successive topmost sheet from essentially the same vertically located pre-feeding position immediately below the retaining stop. The sheet-supporting tray is mounted in a removable holder or magazine by pivoting the tray on a horizontal transverse axis spaced substantially rearwardly from the discharge edge, with the axis located vertically to position the tray in a generally horizontal plane when the discharge edge of an empty tray engages the retaining stop. The stop is also part of the magazine, which further includes bottom, side and end walls, with an open-topped discharge end for providing direct feeding engagement of the starting feed roller with the topmost sheet in the magazine, when such roller is moved to feeding position. The apparatus includes a movable supporting frame for the supply magazine, which can be moved between feeding and loading positions. Magazines with different sizes of sheets can be selectively mounted on the frame with one edge of each such magazine aligned along the same corresponding edge of the path. An auxiliary feed roller having a foam rubber or other foam-like elastomer peripheral surface is positioned above the path to engage the upper surface of each sheet fed forwardly from the supply stack. The apparatus also includes means for removable attachment at an edge of a processing machine, with the auxiliary feed roller above a bed plate of such machine for feeding the sheets across such bed plate. Sheet detecting means and control means are provided to insure desired sequential feeding of successive topmost sheets with controlled spacings along the path, and to turn off the machine automatically when the supporting tray is empty and whenever a sheet fails for any reason to reach a predetermined point along the path within a desired time interval.

United States Patent 11 1 Melby et al.

1 1 Apr. 23, 1974 SHEET FEEDING APPARATUS [75] Inventors: Gordon M. Melby; Richard C.

Young, both of Minneapolis, Minn.

[73] Assignee: Minnesota Mining and Manufacturing Company, Saint Paul, Minn.

[22] Filed: Jan. 19, 1972 [21] Appl. No.: 218,928

Primary ExaminerEvon C. Blunk Assistant Examiner-Bruce H. Stoner, Jr.

Attorney, Agent, or Firm-Alexander, Sell, Steldt & DeLal-lunt [57] ABSTRACT Sheet feeding apparatus is disclosed in which a movably mounted supporting tray supports a stack of sheets at one end of a desired path of feed. The tray has a vertically movable discharge end which is resiliently urged upwardly toward a retaining stop located at a fixed or constant vertical position. Thus the upper surface of the topmost sheet in the stack engages the stop and limits the upward movement of the tray discharge end, so that a common pre-feeding position is defined for the discharge end of each successive topmost sheet. A starting feed roller is mounted above the tray for movement between an upper non-feeding position, in which it is out of engagement with the stack of sheets, and a lower feeding position, in which the roller engages the upper surface of the topmost sheet and starts it along the path. Operating means for moving the starting feed roller from non-feeding to feeding position includes a resilient connection which insures resilient feeding engagement of the roller with the topmost sheet, while the tray discharge edge is urged upwardly with sufficient resilient force to feed the discharge end of each successive topmost sheet from essentially the same vertically located prefeeding position immediately below the retaining stop.

The sheet-supporting tray is mounted in a removable holder or magazine by pivoting the tray on a horizontal transverse axis spaced substantially rearwardly from the discharge edge, with the axis located vertically to position the tray in a generally horizontal plane when the discharge edge of an empty tray engages the retaining stop. The stop is also part of the magazine, which further includes bottom, side and end walls, with an open-topped discharge end for providing direct feeding engagement of the starting feed roller with the topmost sheet in the magazine, when such roller is moved to feeding position.

The apparatus includes a movable supporting frame for the supply magazine, which can be moved between feeding and loading positions. Magazines with different sizes of sheets can be selectively mounted on the frame with one edge of each such magazine aligned along the same corresponding edge of the path.

An auxiliary feed roller having a foam rubber or other foam-like elastomer peripheral surface is positioned above the path to engage the upper surface of each sheet fed forwardly from the supply stack. The apparatus also includes means for removable attachment at an edge of a processing machine, with the auxiliary feed roller above a bed plate of such machine for feeding the sheets across such bed plate. Sheet detecting means and control means are provided to insure desired sequential feeding of successive topmost sheets with controlled spacings along the path, and to turn off the machine automatically when the supporting tray is empty and whenever a sheet fails for any reason to reach a predetermined point along the path within a desired time interval.

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PATENTEDAPR23 I974 11806112 SHEET 5 BF 5 SHEET FEEDING APPARATUS BACKGROUND OF THE INVENTION Processing machines are known in which a plurality of individual answer sheets or cards, which have been previously filled out in response to a questionnaire, may be inserted at a reading station in the machine and automatically scanned to provide a total score or other summary of the test results for each applicant. Such a machineshown, for example, in United States Patent No. 3,518,440 issued June il, 1576. In connection with such machines, there is a need for an improved sheet feeding apparatus which can receive a supply stack of answer cards or sheets, and feed such sheets one at a time, at pre-determined intervals, along a desired path of feed to and through the processing machine. Presently known sheet feeding devices are constructed in a large variety of different ways. Some of these devices feed sheets from the top of the stack, and others from the bottom. In some cases the supporting means for a supply of such sheets is moved into or out of feeding engagement with a feed roller positioned at a relatively fixed location. In other cases a movable feed roller has been moved into or out of engagement with a stack of sheets supported at a substantially fixed position. In some of these devices the feeding engagement between such a feed roller and a sheet to be fed involve undesired variables which contribute to inefficient or inaccurate feeding, particularly where the depletion of a supply stack results in the feeding of successive sheets from somewhat different relative positions in the apparatus.

SUMMARY OF THE INVENTION The present invention provides an improved sheet feeding apparatus in which a movably mounted supporting tray supports a stack of sheets at one end of a desired path of feed and has a vertically movable discharge end which is resiliently urged upwardly toward a retaining stop located at a fixed or constant vertical position. Thus the upper surface of the topmost sheet in such a stack engages the stop and limits the upward movement of the tray discharge end, so that a common pre-feeding position is defined for the discharge end of each successive topmost sheet. A starting feed roller mounted above the tray is moved between an upper non-feeding position in which it is out of engagement with the sheet, and a lower feeding position, in which the roller engages the upper surface of the topmost sheet and starts it along the path. Operating means for moving the starting feed roller from non-feeding to feeding position includes a resilient connection which insures resilient feeding engagement of the roller with the topmost sheet, while the tray discharge edge is urged upwardly with sufficient resilient force to feed the discharge end of each successive topmost sheet from essentially the same or a common vertically located pre-feeding position immediately below the retaining stop. The relative strengths of the resilient upward force on the tray discharge edge and the resilient downward force on the starting feed roller provide a suitable balance of forces to insure timely disengagement of the topmost sheet from the stack and movement of that sheet out from under the retaining stop to start its movement along the desired path.

The sheet supporting tray is preferably mounted in a removable holder or magazine which also includes the retaining stop and resilient means for moving the tray discharge edge upwardly toward the retaining stop. The magazine may include enclosing bottom, side, end and top walls, with an open-top discharge end for providing direct feeding engagement of the starting feed roller with the topmost sheet in the magazine, when such rol' ler is moved to feeding position.

The invention further provides a movable supporting frame for the supply magazine, which can be moved between feeding and loading positions. Magazines of different size, i.e., with different sizes of sheets to be fed, are provided with appropriate positioning means for selectively mounting such magazines on the frame with one edge of each such magazine aligned along the same corresponding edge of the desired path of feed.

The invention further provides an auxiliary feed roller positioned above the path of feed to engage the upper surface of each sheet after the sheet has been fed forwardly from the supply stack. The auxiliary feed roller is provided with a foam rubber or other foam-like elastomer peripheral surface for slipping engagement with the surface of a sheet, while the sheet is still being fed by the starting feed roller, and for firm, nonslipping driving engagement with such sheet, after the sheet has been released by the starting feed roller.

The invention also provides sheet detecting means at a predetermined location along the path, preferably close to the auxiliary feed roller, together with control means connected to insure desired sequential feeding of successive topmost sheets with controlled spacings along the path. The control means insures feeding engagement of the starting feed roller with the topmost sheet in the stack until such sheet has reached the auxiliary feed roller, at which point the control means moves the starting feed roller to non-feeding position. When the leading sheet has moved beyond the auxiliary feed roller or has reached a predetermined distance from the supply stack, the detecting and control means causes movement of the starting feed roller back to feeding position to start another topmost sheet along the path. The invention further provides control circuitry which terminates operation of the sheet feeding device whenever a sheet fails, for any reason, to reach a predetermined point along the path within a desired time interval of operation, for example when the supporting tray has become empty and there is no further topmost sheet to be fed, or when the sheet being fed from the stack becomes jammed.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form a part of this application and in which like reference characters indicate like parts,

FIG. 1 is a perspective view of a sheet feeding apparatus according to the present invention in combination with a further processing machine;

FIG. 2 is an enlarged view from the front of FIG. I, with certain parts shown in section and certain parts broken away, to show details of the sheet feeding apparatus according to the invention;

FIG. 3 is an enlarged partial view of an auxiliary feed roller and detector means in the device of FIG. 2;

FIG. 4 is a view of the sheet feeding apparatus of FIG. 1, taken from the rear of that figure, with parts in section and parts broken away for clearness;

FIG. 5 is a partial top view of the device of FIGS. 2 and 4, showing details of the driving and operating connections for the starting feed rollers and auxiliary feed roller;

FIG. 6 is a side view of the removable supply magazine of FIG. 2, with portions broken away;

FIG. 7 is a top view of the device of FIG. 6, with portions broken away to show details of the positioning means for locating the magazine in the apparatus;

FIG. 8 is a partial side view of the retaining stop in the magazine of FIGS. 2, 6 and 7;

FIG. 9 is a partial top view along the section line 9-9 of FIG. 2, with portions broken away;

FIG. 10 is a rear or end view of the movable supporting frame for the supply magazine, with portions broken away and shown in section on line 10l0 of FIG. 9; and

FIG. 11 is a circuit diagram showing the manner in which the various detecting and control means of the invention are interconnected to insure the desired sequence of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 to 3, a sheet feeding apparatus 11 embodying features of the present invention is used in combination with a further processing machine 12 of any desired type. The machine shown in FIG. 1 is of the type disclosed in the above mentioned Hanson et al patent, in which cards marked with answers to a questionnaire are positioned on the top or bed plate of the machine where they can be moved beneath a reading head 14 for automatically reading the test answers and providing a suitable scoring summary for each answer sheet. After such answer sheets have been scored, they may be deposited in a receiving bin 16 at the opposite end of the machine. guide 17 is provided to establish the desired path of feed of the cards from the sheet feeding apparatus 11 across the bed plate 12 and under the reading head 14. Thus one edge of each sheet will always be located along the common line of guide 17, whether the individual sheets are of the same width or of different widths, with respect to the path of feed.

As more fully shown in FIG. 2 and 3, the sheet feeding apparatus includes a main body 18 with front and top walls 19 and 20. According to one feature of the invention, an extension 21 of the front wall 19 is adapted to project along the desired path of feed so that it overlaps the starting end of the bed plate 13 of processing machine 12. A cooperating bracket 22 on the front wall 19 carries attaching means 23 for firmly but removably attaching the sheet feeding apparatus 1 1 at the starting edge of the bed plate 13 of machine 12. Thus sheets fed from apparatus 11 will move across the top of flange 21 above the bed plate 13 at the start of the desired path, and will be guided by the flange or guide 17 to the desired reading position under head 14, or to feeding means (not shown) on machine 12.

The present invention provides a supply assembly for positioning sheets at one end of the path. This includes a sheet-supporting tray 24 on which a stack of sheets 26 can be supported in a pre-feeding or supply position, as shown in FIG. 2. Resilient spring means 27 urges the discharge end 28 of tray 24 upwardly toward a retaining stop 29 which is located in the sheet feeding apparatus at a predetermined constant vertical position. Thus the stop 29 will engage the upper surface of the topmost sheet 26 stacked on tray 24, when such sheets are urged upwardly by spring 27, to limitthe upward movement of the discharge end 28 and thereby define a common pre-feeding position for the discharge end of each successive topmost sheet. In the form shown in FIG. 2, supporting tray 24 extends rearwardly so that its rear end 31 projects beyond the rear end of the feeding apparatus in a direction opposite to the desired path of feed of the sheets. This rear or remote end of tray 24 may be supported in a manner permitting the desired vertical movement of the forward discharge end 28 of tray 24. In this embodiment the support for the rear portion 31 of the tray is a substantially horizontal, transversely extending shaft at 32, which provides a pivotal axis for the rear end of tray 24. The vertical location of axis 32 is shown at a point such that, when the last sheet 26 has been fed along the path from tray 24, the discharge end 28 of the tray would engage stop 29 and hold the tray in essentially a horizontal position. When a stack of sheets is placed on the tray, the discharge end of the tray is rocked downwardly so that the topmost sheet can be inserted beneath stop 29. Thus the sheets will be inclined somewhat downwardly and forwardly along the direction of feed to help insure the desired location of each sheet at the common prefeeding position, with the forward or discharge ends of such sheets immediately adjacent the rear surface of a suitable front wall or stop 54.

The invention further provides a series of starting feed rollers 33 which are secured to a common transverse shaft 34 carried by the vertically movable forwardly extending lever arms 36. These lever arms 36 are fixed at 37 on a pivotally supported cross shaft 38, so that the lever arms can swing up and down to move the starting feed rollers 33 between an upper nonfeeding position (shown in dotted outline in FIG. 2)

and a lower feeding position (shown in heavy lines in FIG. 2) in which the starting feed rollers engage the upper surface of the topmost sheet and start it along the desired path. As shown in further detail in FIGS. 6 to 8, there are two retaining stops 29 located at opposite front corners of the stack of sheets 26, so that these stops 29 not only limit the upward movement of the topmost sheet, but also provide a forward stop for the extreme lateral edge portions of the topmost sheet. Thus, when starting feed roller 33 is moved to its lower feeding position and engages the topmost sheet, the rotation of rollers 33 will push the top sheet toward the desired path of feed, and the front edge portion of the topmost sheet will buckle slightly in order to permit the sheet to pass between the two retaining stops 29 at the opposite front edges. As shown in FIGS. 7 and 8, the lower surfaces of stops 29 are inclined upwardly and rearwardly from the horizontal (dotted line 131), as shown by dotted extension line 132, at an angle of substantially 10. The opposite inwardly facing edges of stops 29 are inclined angularly toward each other along the direction of feed, as shown at 133, to facilitate the release of the topmost sheet.

The discharge end of the topmost sheet will then pass above the top edge 59 of front retaining wall 54, and the sheet will successively pass over the inclined leading edge 39 of flange 21, then across flange 21 above bed plate 13, and on across the processing machine 12.

An auxiliary feed roller 41 is spaced forwardly along the path of feed for engaging the upper surface of a sheet which has been started along the path. This auxiliary feed roller is carried by a rotary transverse shaft 42 and is rotated in a direction to continue the feeding movement of the sheet along the path. The leading edge of each sheet will then pass down over the tapered forward end 43 of flange 21 into direct engagement with the upper surface of bed plate 13. At this particular location, the invention further provides a detecting means having a movable detecting arm 44 which normally rests in a lower position, but which will be lifted slightly by the engagement of a sheet, when the leading edge of the sheet passes beneath detector 44.

As shown in FIG. 3, detector arm 44 is connected to a suitable precision switch 46 which is connected in an appropriate control circuit, as further described herein, to achieve the desired control and sequence of operation. Switch 46 is adjustably mounted in the apparatus by a pivot pin 47 and by a pin and slot connection 48, 49, so that the switch can be secured in a range of desired positions to provide the desired movement of detector arm 44 for sheets of different thickness or flexibility.

In operation, when the sheet feeding apparatus is loaded with a stack of sheets 26 and is first energized by operation of a starting switch, the starting feed rollers 33 will be rotated in a clockwise direction as viewed in FIG. 4 and will be moved to the lower feeding position shown in that view, so that the topmost sheet will be started along the path. The forward or discharge end of the sheet will reach the auxiliary feed roller 41, before the rear of the sheet has passed beyond the starting feed rollers 33. The auxiliary feed roller 41 is preferably made of foam rubber or another foam-like elastomeric material, so that it has a relatively resilient peripheral surface to engage the upper surface of each sheet. Auxiliary feed roller 41 will be driven with a peripheral speed at least as great as that of starting feed roller 33, and preferably at a greater speed, in order to provide the desired spacing between successive sheets along the path. When the roller 41 moves at higher speed, its periphery will be in resilient slipping engagement with the top of a sheet, as long as the speed of movement of that sheet is limited to the peripheral speed of starting feed rollers 33.

When the leading edge of the sheet engages the detector arm 44, however, the control circuitry of the apparatus will cause upward movement of starting feed rollers 33 to their non-feeding position, so that rollers 33 will no longer control the speed of movement of the sheet along the path. At this point, the resilient peripheral engagement of auxiliary feed roller 41 will provide a firm gripping or driving engagement with the sheet and will move the sheet along the path at a speed corresponding essentially to the peripheral speed of roller 41. Then, as soon as the sheet has progressed into the processing machine 13 and been further fed by that machine along the desired path, the rear or trailing edge of the sheet will pass beyond the detector arm 44, so that the arm can again drop. The control circuitry will then cause movement of starting feed rollers 33 back to their lower feeding position to start the movement of a following sheet along the path, in the same manner just described.

According to a further feature of the invention, the supporting tray 24 for the supply of sheets 26, the resilient spring means 27, and the retaining stops 29 are connected to each other as parts of a removable supply magazine 51, as shown in detail in FIGS. 2, 6 and 7. Supply magazine 51 thus includes one or more enclosing walls, such as bottom wall 52, side walls 53, front wall 54 and rear wall 56. A top wall could be provided at 57 over part of the magazine, but at least the forward end of the magazine must be open at the top, as shown in 58, to provide for direct feeding engagement of the starting feed rollers 33 with the topmost sheet in the magazine, when the starting feed rollers move to feeding position. The height of the front wall 54 must also be limited, so that the upper edge of this wall at 59 is somewhat below the lower surface of the retaining stops or corner nips 29 to permit feeding movement of the topmost sheet forwardly along the path from the magazine 56.

To facilitate the feeding of sheets of different sizes, and to facilitate loading and unloading of magazines such as 51, the invention provides a moveable supporting frame on which an individual magazine of desired size can be supported for movement between the feeding position and a magazine loading position. Thus, as shown particularly in FIGS. 9 and 10, the flat moveable supporting frame 61 is provided with downwardly projecting guide posts 62 which guide the frame 61 for movement longitudinally in slots 63 in a fixed cross frame member 64. Cross frame member 64 is secured at 66 to the inner supporting sidewalls 18a of the apparatus. Member 64 also carries longitudinal supporting slides 67 which are made of plastic material which provides a convenient longitudinal slide for the moveable supporting frame 61. A flange 69 at the rear of frame 61 serves as a handle to move the frame 61 longitudinally from the feeding position shown in FIG. 9 to a rearwardly retracted loading position. Thus a magazine can be placed on the supporting frame 61 when the frame is moved to the rear of the sheet feeding apparatus, out from under the starting feed rollers 33. When a magazine has been placed on the moveable frame 61 at that point, handle 69 can be pushed to move the frame 61 and the magazine 51 supported thereon forwardly along the path of feed into the initial feeding position.

The invention also provides means for removably supporting magazines of different size on the moveable supporting frame 61. For this purpose, positioning members 71, 72 and 73 are located transversely across the forward or discharge end of the frame member 61. These positioning posts are located in such a way that magazines of different size can be engaged with different pairs of the posts, depending on the particular sizes of the sheets which are to be fed for processing in machine 12 at any given time. For example, a magazine 51, of the type shown in FIGS. 2 and 6, could have a width transversely of the direction of feed which would substantially cover the entire support frame member 61. Such a magazine would have interengaging means adapted to fit over all of the positioning posts 71, 72 and 73, and firmly engage at least two of such posts to make sure the magazine remains in the desired feeding position when the frame member 61 is in its forward position. When a narrower magazine 51 is to be used, it could be engaged with only two of the positioning posts 71 and 73, so that the right edge of the magazine as viewed in FIGS. 9 and 10 would be in alignment with the right edge of the sheet feeding apparatus and thus in position to be fed along the guide 17 of the processing machine in FIG. 1. Such a narrow magazine, however, would extend laterally from the right edge of moveable frame 61 to a position such as that indicated by the dotted line 74 in FIG. 9. Such a half width magazine is shown in a top enlarged view by way of example in FIG. 7. The magazine includes appropriately located clips 76 in its bottom wall 52, and these clips are spaced on each side of the resilient spring means 27 of such a unit at locations adapted to engage posts 71 and 73 in FIGS. 9 and 10. For a full width magazine, clips such as 76 would be spaced corresponding to posts 71 and 72 in FIGS. 9 and 10, and the bottom wall of such a magazine could have merely an opening into which post 73 could project, without necessarily being engaged by a retaining clip on the bottom wall. Post 73 is offset from the center line of the moveable frame 61 in order that it will project into the bottom wall of a full-width magazine at a point out of alignment with the centered resilient spring 27 for the supporting tray 24 of such a magazine.

The driving mechanism for the starting feed rollers and auxiliary feed roller, and the operating mechanism for moving the starting feed rollers between nonfeeding and feeding position, is shown in detail in FIGS. 4 and 5. Thus in FIG. 5, the starting feed rollers 33 are rigidly secured to rotating cross shaft 34 which is rotably mounted in the supporting lever arms 36 and 36A. These arms are secured to rotate with the supporting shaft 34 which extends transversely between the inner sidewalls 18A of the apparatus. A coil spring 77, which engages the frame and one of the lever arms 36, normally urges the lever arms and rollers 33 upwardly as a unit to their non-feeding position. Shaft 34 has a drive pulley 78 at its right end in FIG. 5, and this drive pulley is engaged by a drive belt 79 driven from an intermediate roller 81, which is freely rotatable on the right end of the supporting shaft 34 for lever arms 36 and 36A. A similar driving pulley 82 on the right hand end of shaft 42 serves to drive the auxilliary feed roller 41 by means of a drive belt 83. Belt 83 is driven from a slightly larger drive pulley 84 which rotates as a unit with pulley 81. The pulley assembly 81 and 84 also includes another drive pulley member 86 which rotates as a unit with these parts. Drive pulley 86 is engaged by a drive belt 87 driven from the drive pulley 88 (FIG. 4) of a driving motor 89.

In this manner, when the motor 89 is running, it will constantly rotate all of the drive pulley members 81 and 84 through associated pulley 86. These drive pulleys in turn will constantly rotate the starting feed roller 33 and the auxiliary feed roller 41. The relative sizes of the respective pulleys are chosen in such a manner that the peripheral speed of the auxiliary speed roller 41 will be at least as high as the peripheral speed of the starting feed rollers 33. Preferably, as shown by the relative pulley sizes in FIG. 4, the pulley ratios will be such that the peripheral speed of auxiliary roller 41 will be somewhat higher than the peripheral speed of starting feed rollers 33. Thus when a leading sheet or card is engaged by auxiliary roller 41 and is released from starting feed rollers 33 by the movement of such rollers to their upper non-feeding position, the auxiliary roller 41 can push the card ahead at a greater rate and thus achieve a greater predetermined spacing between successive sheets or cards. The foam-like peripheral surface of auxiliary roller 41 further permits slipping engagement, as described, so that even before the feed roller 33 releases a sheet, the auxiliary feed roller tends to help pull the leading sheet from the stack due to the resilient frictional slipping engagement between the auxiliary roller 41 and the upper surface of such sheet.

The springmember 77 (FIG. 5) normally holds the lever arms 36 and 36A and shaft 34 in the upper nonfeeding position of starting feed rollers 33. The rotation of all the pulleys 81, 84 and 86 in a sheet feeding direction also tends to rotate shaft 34 to the upper nonfeeding position of starting feed rollers 33. Shaft 34 includes at its right hand end an operating lever 91 which is securely keyed to the shaft through a bushing 92 and retaining screw 93. The lower end of operating lever 91 is secured at 94 to a resilient spring connection 95, the other end of which is secured to the longitudinally moveable core 96 of a solenoid 97. When the coil or winding 98 of the solenoid is energized, core 96 will be drawn to the left in FIG. 4, tensioning the resilient spring connection sufficiently to rock lever arm 91 and starting feed rollers 33 to their feeding position in engagement with the topmost sheet 26 in the supply stack. When the solenoid coil 98 is de-energized, spring 77 on shaft 34 has sufficient resilience to pull the parts to the upper non-feeding position. The extent of such upward retraction is determined by an adjustable stop 99 which may be located at any convenient part of the assembly, but which is illustrated in FIG. 4 as engaging and limiting the forward movement of the solenoid core 96.

The various parts just described are connected through appropriate electrical circuitry to achieve the desired mode of operation. A suitable circuit diagram is shown in FIG. 11, in which the circuit is connected to supply lines 101 and 102 of a suitable l 10 volt A.C. supply. A normally open starting switch 103 is momentarily closed to start the operation of the unit. When this switch is closed, it completes a circuit from line 101 to line 102 through a normally closed stopping switch 104, a normally closed relay contact 105 and the energizing coil 106 of a holding relay K-l. The holding relay closes contacts 107 to establish a holding circuit and operating circuit from line 101 through contacts 107, branch line 108, the closed stopping switch 104, and contacts 105 and relay coil 106. Thus coil 106 will continue to hold contacts 107 closed to maintain the circuit during normal operation. This closing of the circuit at contacts 107 also completes a parallel circuit through the motor 89 so that the motor will run continuously and drive the respective feed rolls continuously, until otherwise interrupted. The motor circuit is completed through the line 109 to line 102.

Supply line 101 is further connected through a branch line 111 and a bidirectional thyristor 112 to another parallel branch line 113 which includes the solenoid winding 98. A further branch line 114 in parallel with solenoid line 113 includes a diode 115, in series with a resistance 116, and parallel branch lines including condensor 117 and the coil 118 of a second relay K-2 which controls the contacts 105 in the original holding circuit. The values of resistor 116, condensor 117 and the resistance of coil 118 are chosen to provide a desired time constant. Thus when current is flowing through all of the branches 109, 113 and 114, condensor 117 will gradually be charged. After the predetermined time, the relay coil 118 will have sufficient voltage drop across it to be energized to open its relay contacts 105 and shut off the apparatus in case a sheet does not reach the detector arm 44 of control switch 46 within the predetermined time.

The precision switch 46 is connected to control the switching condition of the bidirectional thyristor 112. For this purpose, the first main terminal 119 of the thyristor is connected to the gate 122 of the thyristor through a resistor 123 and the detecting switch 46 via lines 124 and 126. Thus when the switch 46 is normally closed and awaiting the arrival of a sheet, the connection between main terminal 1 19 and gate 122 maintains the thyristor 112 in a current-transmitting or on" condition to complete the parallel circuits through lines 113 and 114. When the leading edge of a sheet is fed by the starting feed rollers 33 to the auxiliary feed roller 41, so that the edge of the sheet moves detector arm 44 and opens switch 46, the opening of the connection between thyristor terminal 119 and its gate 122 permits the thyristor to switch to a non-conducting or off condition, so that no current is transmitted from its second main terminal 121 to its terminal 119 and the parallel branch lines 113 and 114. At this point, the solenoid coil 98 is deenergized, and the starting feed rollers 33 will move upwardly to their non-feeding position. Also at this time the condensor 1 17 will have an opportunity to be at least partially discharged through the relay coil 118, in preparation for another timing cycle.

Once the sheet has passed the detector arm 44, so that switch 46 can return to its normally closed position, the reconnection through resistor 123 of thyristor terminal 119 and its gate 122 restores the thyristor to a conducting or current transmitting condition. The solenoid winding 98 is thus energized, and the starting feed rollers are pulled down to their feeding position to start the movement of the next topmost sheet from the supply stack. When the last sheet has been fed, the absence of a further sheet will leave the switch 46 in its normally closed position, and the gradual build-up of a charge on condensor 117, after the pre-selected time interval, will actuate relay coil 118 and open contacts 105 to stop the machine.

The machine can also be stopped manually at any time by operation of the normally-closed stopping switch 104, which momentarily opens the holding circuit through relay coil 106 and permits its relay contacts 107 to become open to break all of the circuits involved including the holding circuit, the motor cir' cuit, the solenoid circuit and the time delay circuit.

An improved sheet feeding apparatus and control system have accordingly been described in the foregoing specification, together with some of the ways of practicing the invention. The description includes the best mode presently known for putting the invention into practice. A sheet feeding apparatus constructed in the manner herein described offers the indicated operating advantages of smooth and controlled feeding of successive sheets from the top of a supply stack, with desired control over the relative spacing of successive sheets along the path of feed, and with the provision of safety means in the form of a time delay device to shut off the operation of the machine if, for whatever reason, a sheet fails to reach the detecting means at the point where such sheets are being transferred to a suitable processing machine or are otherwise being discharged from the sheet feeding apparatus of this invention.

We claim:

1. Sheet feeding apparatus for successively feeding individual sheets along a desired path comprising, in combination:

a supply assembly for positioning a supply of sheets at one end of the path, the supply assembly includmg:

a sheet-supporting tray movably mounted in said assembly for supporting a stack of sheets, said tray having a vertically movable forward discharge end from which sheets are to be fed along the path;

a retaining stop on said assembly above the discharge end of the tray, said stop being located at a predetermined constant vertical position for engaging the upper surface of the topmost sheet on the tray and limiting the upward movement of the discharge end, thereby defining a common pre-feeding position for the discharge end of each successive topmost sheet; and

resilient means urging the discharge end of the tray upwardly toward the retaining stop;

a starting feed roller mounted above the supply assembly near the discharge end for movement between an upper non-feeding position and a lower feeding "position in which the starting feed roller engages the upper surface of the topmost sheet and starts it along the path;

motor means operatively connected for rotating the starting feed roller in a sheet feeding direction;

operating means for moving the starting feed roller between non-feeding and feeding positions; and

an auxiliary feed roller spaced forwardly along the path for engaging the upper surface of a sheet which has been started along the path, said motor means being operatively connected for rotating the auxiliary feed roller in a sheet feeding direction at a peripheral roller speed at least as high as the peripheral roller speed of the starting feed roller, and said auxiliary feed roller having a foam-like elastomer peripheral surface for resilient slipping engagement with each sheet until such sheet is disengaged from the starting feed roller and for firm driving engagement with each sheet thereafter.

2. Sheet feeding apparatus according to claim 1 in which the peripheral speed of the auxiliary feed roller is greater than that of the starting feed roller, said apparatus also including detector means for detecting the arrival of a sheet in engagement with the auxiliary feed roller, and control means connecting the detector means and operating means for moving the starting feed roller to non-feeding position when a sheet has been engaged by the auxiliary feed roller and for moving the starting feed roller to feeding position when a preceding sheet has passed beyond the auxiliary feed roller.

3. Sheet feeding apparatus for sucessively feeding individual sheets along a desired path comprising, in combination:

a supply assembly for positioning a supply of sheets at one end of the path, the supply assembly includmg:

a sheet-supporting tray movably mounted in said assembly for supporting a stack of sheets, said tray having a vertically movable forward discharge end from which sheets are to be fed along the path;

a retaining stop on said assembly above the dischrage end of the tray, said stop being located at a predetermined constant vertical position for engaging the upper surface of the topmost sheet on the tray and limiting the upward movement of the discharge end, thereby defining a common pre-feeding position for the discharge end of each successive topmost sheet; and

resilient means urging the discharge end of the tray upwardly toward the retaining stop;

a starting feed roller mounted above the supply asmotor means operatively connected for rotating the starting feed roller in a sheet feeding direction;

operating means for moving the starting feed roller between non-feeding and feeding positions; and

attaching means for removable connection of the apparatus at an edge of a bed plate of a processing machine in which sheets are to be fed across the bed plate for processing by said machine, the attaching means positioning the sheet feeding apparatus at a location directing sheets fed along said path by the starting roller onto the bed plate, and

said apparatus having an auxiliary feed roller spaced forwardly along said path at a location above such bed plate for engaging the upper surface of a sheet which has been started along said path above the bed plate, said motor means being operatively connected for rotating the auxiliary feed roller in a sheet-feeding direction at a peripheral roller speed greater than the peripheral roller speed of the starting feed roller, and said auxiliary feed roller having a resilient peripheral surface for resilient slipping engagement with each sheet until such sheet is disengaged from the starting feed roller and for firm frictional driving engagement with each sheet thereafter. 

1. Sheet feeding apparatus for successively feeding individual sheets along a desired path comprising, in combination: a supply assembly for positioning a supply of sheets at one end of the path, the supply assembly including: a sheet-supporting tray movably mounted in said assembly for supporting a stack of sheets, said tray having a vertically movable forward discharge end from which sheets are to be fed along the path; a retaining stop on said assembly above the discharge end of the tray, said stop being located at a predetermined constant vertical position for engaging the upper surface of the topmost sheet on the tray and limiting the upward movement of the discharge end, thereby defining a common pre-feeding position for the discharge end of each successive topmost sheet; and resilient means urging the discharge end of the tray upwardly toward the retaining stop; a starting feed roller mounted above the supply Assembly near the discharge end for movement between an upper non-feeding position and a lower feeding position in which the starting feed roller engages the upper surface of the topmost sheet and starts it along the path; motor means operatively connected for rotating the starting feed roller in a sheet feeding direction; operating means for moving the starting feed roller between nonfeeding and feeding positions; and an auxiliary feed roller spaced forwardly along the path for engaging the upper surface of a sheet which has been started along the path, said motor means being operatively connected for rotating the auxiliary feed roller in a sheet feeding direction at a peripheral roller speed at least as high as the peripheral roller speed of the starting feed roller, and said auxiliary feed roller having a foam-like elastomer peripheral surface for resilient slipping engagement with each sheet until such sheet is disengaged from the starting feed roller and for firm driving engagement with each sheet thereafter.
 2. Sheet feeding apparatus according to claim 1 in which the peripheral speed of the auxiliary feed roller is greater than that of the starting feed roller, said apparatus also including detector means for detecting the arrival of a sheet in engagement with the auxiliary feed roller, and control means connecting the detector means and operating means for moving the starting feed roller to non-feeding position when a sheet has been engaged by the auxiliary feed roller and for moving the starting feed roller to feeding position when a preceding sheet has passed beyond the auxiliary feed roller.
 3. Sheet feeding apparatus for sucessively feeding individual sheets along a desired path comprising, in combination: a supply assembly for positioning a supply of sheets at one end of the path, the supply assembly including: a sheet-supporting tray movably mounted in said assembly for supporting a stack of sheets, said tray having a vertically movable forward discharge end from which sheets are to be fed along the path; a retaining stop on said assembly above the dischrage end of the tray, said stop being located at a predetermined constant vertical position for engaging the upper surface of the topmost sheet on the tray and limiting the upward movement of the discharge end, thereby defining a common pre-feeding position for the discharge end of each successive topmost sheet; and resilient means urging the discharge end of the tray upwardly toward the retaining stop; a starting feed roller mounted above the supply assembly near the discharge end for movement between an upper non-feeding position and a lower feeding position in which the starting feed roller engages the upper surface of the topmost sheet and starts it along the path; motor means operatively connected for rotating the starting feed roller in a sheet feeding direction; operating means for moving the starting feed roller between non-feeding and feeding positions; and attaching means for removable connection of the apparatus at an edge of a bed plate of a processing machine in which sheets are to be fed across the bed plate for processing by said machine, the attaching means positioning the sheet feeding apparatus at a location directing sheets fed along said path by the starting roller onto the bed plate, and said apparatus having an auxiliary feed roller spaced forwardly along said path at a location above such bed plate for engaging the upper surface of a sheet which has been started along said path above the bed plate, said motor means being operatively connected for rotating the auxiliary feed roller in a sheet-feeding direction at a peripheral roller speed greater than the peripheral roller speed of the starting feed roller, and said auxiliary feed roller having a resilient peripheral surface for resilient slipping engagement with each sheet until such sheet is disengaged from the starting feed roller and for firm frictional driving engagement witH each sheet thereafter. 